I have no opinion really @Verysad1978 as I can't imagine what it's like to have an ex at all, let alone spend Christmas with them. I've never actually broken up with anyone properly. I've not had any long-term relationship before DH, (who I have been with for around 30 years.) I only had four boyfriends before him that lasted about three to six weeks .. And that was in my late teens/early 20s. None of them meant much to me, and I didn't care when we split.
I know a woman right now who's in her late 40s and who's got two teenage children, and had been married 22 years when her husband left her around early to mid 2022 for another woman. He left her in their social housing property with their two children. Didn't give her any money or anything, and she was left to cope alone, scratching around for extra hours to try and pay the rent and bills, and feed and clothe the kids.
Last Christmas he was with his other woman - while she had to get into debt to buy some presents for the kids. Come spring this year, she met a man who is actually quite well off. He treats her a lot, takes her for meals, takes her on holidays abroad, spends money on the kids, and thinks the world of her - and her kids. He is divorced himself after 17 years. Ex wife left him for another man 6 years ago, moved away. Never had any children.
Anyway, come August/September this year - her husband's other woman left him/threw him out and he is housesharing at the moment with 3 other men, just has a bedroom to himself. The other woman actually contacted this woman I know and said, 'will you have him back?' She said, 'yeah, right. Sure I'll have him back!' 😆 LOL as if!!! Her new man is 100X better. She'd actually managed to get her ex's name off the tenancy - and it was all in her name now and she refused to have him back ...
Nevertheless, her kids were so upset that their dad was going to be on his own this Christmas. He has only got a brother that he doesn't speak to and his parents have passed away ... So she let him come and spend Christmas with her and the kids and her new man! So not only is this a woman having her ex around, but her new man is there. Her ex is staying 3 days! It was actually her new man's idea too! For her ex to come! 'Did it for the kids' he said.
But yeah tl;dr some people do still get on once the dust has settled. I doubt she would have had him anywhere near if she had not met her new man though!